> Reddit's biggest problem is that the big subreddits are incredibly homogenous, and the small ones incredibly slow.

There's definitely middle ground though. /r/DepthHub is pretty good at aggregating solid comments. And there's good debate on subs like /r/ChangeMyView and /r/NeutralPolitics. Admittedly, these subs don't refresh as fast as /r/worldnews, but there's usually new content every day.